Construction of exploratory borings
Summary of water district standards

Permit and license requirements
A permit is required for any boring more than 45 feet in total depth regardless of groundwater depth. There are no fees for permits. All permit applications must have original signatures. Permits are required for all exploratory borings greater than 45 feet in depth. Please call (408) 265- 2607, extension 2660, for permit applications or download one [PDF]. Drilling contractors must have a current California C-57 or C-61 contractor's license.

One permit covers all exploratory borings on the same assessor's parcel. Separate permits are required for each assessor's parcel even if multiple parcels are considered the same site. Cone penetrometers and hydropunches holes are classified as exploratory borings and must be permitted as such.

Destruction of exploratory borings
All borings must be properly destroyed by backfilling with acceptable sealing materials. No soil cuttings may be used for backfilling boreholes. All borings should be backfilled within 24 hours of termination of testing.

Acceptable sealing materials
Acceptable sealing materials are 27 sack neat cement (four 94-pound bags/55-gallon drum), 10 sack cement sand grout, or hydrated high solids 20 percent bentonite slurry. No bentonite chips or pellets may be used to backfill borings.

Placement of sealing materials
Free fall of sealing material is not allowed if greater than 30 feet or if more than 3 feet of standing water exists in borehole. A tremie pipe must be used to place the cement sealing material if exploratory boring is over 30 feet deep or if more than 3 feet of standing water exists in borehole. Exploratory borings located in Geological Setting Zone 4 (bedrock) may be backfilled with borehole cuttings from total depth of the boring up to a depth of 50 feet from surface grade. The top 50 feet of the borehole must be backfilled with above described sealing materials.